Certified Rhythm Analysis Technician (CRAT) Practice Exam

The P wave on an electrocardiogram (ECG) signifies the depolarization of the atria, which is the first phase in the heart's electrical cycle. During this phase, the electrical impulse generated by the sinoatrial (SA) node travels through the atrial muscle, leading to contraction and the subsequent filling of the ventricles. The P wave reflects this electrical activity and is crucial in indicating the heart’s rhythm and identifying any potential issues with atrial conduction.

The other structures mentioned—ventricles, Bundle of HIS, and Purkinje fibers—are involved in different phases of the cardiac cycle. The ventricles are activated later in the sequence and correspond with the QRS complex, which represents ventricular depolarization. The Bundle of HIS and Purkinje fibers convey impulses to the ventricles but do not contribute to the P wave, which is specifically associated with atrial activity. Hence, recognizing that the P wave is focused on the atria helps provide a clearer understanding of its role in the overall electrical conduction system of the heart.